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The zygote undergoes a series of cell divisions (called cleavage) to form a structure called a morula. The morula develops into a structure called a blastula through a process called blastulation. The blastula develops into a structure called a gastrula through a process called gastrulation.
The zygote is the earliest developmental stage. In humans and most other anisogamous organisms, a zygote is formed when an egg cell and sperm cell come together to create a new unique organism. The formation of a totipotent zygote with the potential to produce a whole organism depends on epigenetic reprogramming.
In biological terms, the development of the human body entails growth from a one-celled zygote to an adult human being. Fertilization occurs when the sperm cell successfully enters and fuses with an egg cell (ovum). The genetic material of the sperm and egg then combine to form the single cell zygote and the germinal stage of development commences.
As the zygote undergoes cell division to form two, then four, then eight and then 16 cells (typically by day four after fertilization), it becomes a ball of cells called a morula. During these cellular divisions, the zygote remains the same size, but the number of cells increase.
The first cell division of a zygote is asymmetric, resulting in an embryo with one small cell (the apical cell) and one large cell (the basal cell). [22] The small, apical cell will eventually give rise to most of the structures of the mature plant, such as the stem, leaves, and roots. [23]
Various disorders can arise from defects in the fertilization process. Whether that results in the process of contact between the sperm and egg, or the state of health of the biological parent carrying the zygote cell. The following are a few of the diseases that can occur and be present during the process.
The male and female gametes combine to produce the zygote cell. In multicellular organisms, the zygote subsequently divides in an organised manner into smaller more specialised cells, so that this new individual develops into an embryo. In most animals, the embryo is the sessile initial stage of the individual life cycle, and is followed by the ...
There are also several other differences from embryogenesis in lower chordates. One such difference is that in mammalian embryos development of the central nervous system and especially the brain tends to begin at earlier stages of embryonic development and to yield more structurally advanced brain at each stage, in comparison with lower ...